Blasting explosive package



June 26, 1951 H. R. WRIGHT ETAL BLAs'rING ExPLosIvE PACKAGE Filed Sept. 29, 1948 ,3F/G3. I/l/I/ In venters: Zlrld Reginald; Wrlgh, william /zydon allan QM. M @L MA ttorney Patented June 26, 1951 BLASTING EXPLOSIVE PACKAGE Harold R. wright, west Kiibriae, and William G. Allan, Saltcoats, Scotland, assignors to Imperial Chemical Industries Limited, a-corporation of Great Britain Application September 29, 1948, Serial No. 51,828 In Great Britain November 19, 1947 3 Claims. 1

The present invention relates to improvements in columnar blasting explosive packages of the kind wherein a rigid tubular sheath of cardboard or the like holds a succession of detonating explosive cartridges in alignment along its length so they will-transmit a detonation from one to another along the column.

For blasting operations under conditions 'where considerable hydrostatic pressures are encountered as in submarine blasting, seismic, or deep well blasting the available range of explosive compositions that can be relied upon to detonate at high velocity when used under such pressure is somewhat more limited than for blasting operations conducted ear the ground surface. The

compositions use for instance cast or compressed compositions based on aromatic polynitrocompounds, solid explosive nitricvesters or nitramines either alone or in admixture are commonly of a rigid consistency, and they are usually less easy to in`tiate than nitroglycerine explosives. For this reason it may be necessary to .interpose a booster of a more sensitive detonating explosive between the detonator and the main charge of the detonating explosive. The main charge or the booster as the case may be is shaped to accommodate a detonator.

It is frequently required in such situations to employ columnar explosive chargesv built up from a number of explosive cartridges in detonation transmission relationship and to load the cartridges into the borehole already aligned in a rigid tube, which can be introduced bodily into the borehole, but it will not in general be known to the manufacturer how many cartridges of a given weight will be required in the column for the particular yshot to be red.

It is known to provide blasting explosive package elementswherein each cartridge is contained in a rigid tube provided with an external screw thread Whichcan be joinedv to a similar element by means of an internally threaded rigid sheath so as to build up a continuous rigid sheathed column containing a number of cartridges in transmission relationship, but the smaller the weight of explosive likely to be required in each element the more expensive it would be to package each one in such a manner, and the greater would be the opportunity for the elements in the column to become unscrewed or get out of alignment.

It would therefore be desirable to provide a columnar blasting explosive package containing a number of cartridges comprising a rigid high velocity explosive composition in le in a unitary it, to the inner wall of which are adhesively at-` tached a number of similarly oriented cartridges of rigid detonating explosive each shaped at one end to accommodate a detonator, whereof at least the terminal portions so shaped consist of an explosive sensitive to initiation directly by a detonator, said cartridges being separated from one another in the tube by deformable spacing members each covering only a portion of the end surface of each cartridge and being of insumcient thickness to lprevent the transmission of detonation from one cartridge to the next, the tube being distinctively marked on its exterior wall opposite each spacing member.

The marks serve to indicate to the operator the line around which the tube should be cut in order to divide it at the correct position to permit insertion of a detonator. In forming the individual cartridges the main portion of the explosive if not sulcently sensitive to be directly initiated by a detonator, may conveniently be cast around a pellet booster, the booster explosive being directly sensitive to a detonator. Each explosive charge may be contained in a cup of paper or other suitable material with the booster, if present, at one end. The cartridges may be located in the rigid tube by meansA of a each cartridge. The rigid tube is desirably made of cardboard, thick pasteboard, thick paper or like rigid material that can be cut by means of a knife, and is marked opposite the discs separating the individual cartridges with indentations or surfacemarks. One or both ends. of `the tube may be turned over, provided access is left for a detonator to be inserted into the end of the terminal cartridgeshaped to accommodate it, e. g. by leaving the turned over end open at the middle or by providing an easily rupturable end closure. Such turning over assists in the support of the cartridges within the tube.

It will be understood that if desired the exterior of the columnar blasting explosive package may be provided with means facilitating its junction to another similar columnar blasting with a tubular external coupling member made with a helical slot running along its internal surface. Figure 4 is an end elevation of the assembly illustrated in Figure 3 and Figure 5 is an enlarged detail in axial section of one of the cartridges accommodated in the package illustrated in Figure l and in the assembly illustrated in Figure 3.

Referring to Figure 1, the rigid waxed cardboard tube I has an open helical ridge 2 formed along its outer surface and has a cylindrical inner surface. Terminal portions of its length are turned over leaving a central hole around 6, as is best seen at 3 in Figures 2, 3, andA 4. A series of marks 4, seen only in Figure 1. are located so as to lie exactly over a series of annular felt spacing discs 5 seen in Figure 3 separating the explosive cartridges C from one another. The external coupling tube I has a helical slot 8 running along its internal surface in which the heli-` cal ridge 2 can run as seen in Figures 3 and 4.

Each explosive cartridge C, as best seen in Figure 5, has a thin paper container 9 folded over at one end into the form of a cup into which there is laid a thin paper disc I cemented to the base of a pellet primer II axially channeled to accommodate a detonator not shown. The primer I has a thin paper disc I2 covering its other end, and a charge I3 of a high velocity rigid explosive is cast into the paper cup around the pellet booster. The explosive charge I3 becomes rigid when it solidifles. It may advantageously consist of a mixture of TNT and tetryl `in the proportions 75:25 by weight, and the pellet primer may be made of compressed tetryl, PETN or cyclotrimethylene trinitramine.

The exterior surface of each cartridge C is smeared with a cement not shown in the drawing, e. g. one based on nitrocellulose, capable of adhering to the waxed inner surface of the tube I, only one of the ends of which is turned over at this stage. The rst cartridge is then loaded into the tube I so as to rest on the turned over end of the tube. and the annular felt spacing disc is laid over it. The next cartridge is then introduced so as to rest in the same orientation over the aforesaid felt spacing disc, and so forth until the required number of cartridges and spacing discs have been introduced. The remote end of the tube I is then turned over.

If it is required to employ only say two of the five cartridges in the package, the tube I is cut through by an operator at the mark lying over the spacing disc between the second and third cartridges, so as to subdivide the package between these two cartridges. The felt spacing disc thus exposed is removed and discarded. If it is required to use seven cartridges, one of the packages is similarly subdivided between the second and third cartridge and the smaller of the resulting cut packages is coupled with an undivided package provided with a screw sheath as shown in Figure 3, by screwing the sheath relative to the packet so as to engage the thread on the surface of the cut package abutted endwise to said undivided package.

An electric detonator may be inserted through the thin paper coverings ofthe terminal pellet booster into the channel thereof. When the borehole is loaded and the detonator is fired this booster will detonate and initiate the detonation at high velocity of the explosive charge cast around it. and this in turn will initiate the detonation of the nextv booster, the distance between the cartridges separated by the spacing discs being so restricted as vto ensure the detonation being transmitted from cartridge to, cartridge.

We'claim:

1. A columnar blasting explosive package comprising a rigid tube of material subdivisible into lengths by cutting, a plurality of similarly oriented cartridges superposed one on the other and lying within said rigid tube, each of said cartridges comprising a cast detonating explosive adapted to receive at one. end thereof a detonator and each of said cartridges being spaced from each of said other cartridges by an annular disc of felt material, and distinctive markings on the external portion of said tube in positions corresponding to said annular spacing means.

2. A columnar blasting explosive package comprising a rigid tube of,A material subdivisible into lengths by cutting. a plurality of similarly oriented cartridges superposed one on the other and lying within said rigid tube. each of said cartridges comprising a cast detonating explosive adapted to receive at one end thereof a detonator and each of said cartridges being spaced from each of said other cartridges by an annular disc, distinctive markings on the external portion uf said tube in positions corresponding to said annular spacing means, and means for facilitating the junction of the exterior of said rigid tube of said explosive package to another similar package in order to form a longer rigid column.

3. A columnar blasting explosive package as set forth in claim 2 wherein said junction means comprises a helical ridge running the length of said rigid tube and an external coupling tube adapted to cooperate with said helical ridge.

HAROLD R. -WBIGHT WILLIAM G. ALLAN.

REFERENCES CITED I The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,406,844 Gelm Feb. 14, 1922 1,431,774 Bowman Oct. 10, 1922 1,587,356y Riebeth June l, 1926 2,078,298 White Apr. 27, 1937 2,129,508 Slusser Se t. 6, 1938 2,353,739 -Magill J y 18, 1944 2,403,488 Bennett July9, 1946'v 2,429,079 Smith Oct. 14, 1947 2,448,658 Carey Sept. 7, 1948 OTHER REFERENCES War Department Field Manual FM 5-25 re Explosives and Demolitions. dated February 29, 1944. Printed by United States Government Printing Office. Pages 5 and 6. (Copy in Division 70.) 

